The present invention relates, in general, to electrical watthour meters and, specifically, to electrical watthour meter sockets, and more specifically, to meter sockets and bypass devices for use with current transformers.
In the electric utility industry, watthour meters are employed to measure electrical power consumption at a residential or commercial building establishment. A cabinet is typically mounted on an outside wall of the residence or building and contains a meter socket having pairs of line and load contacts which are connected to electric power line conductors extending from the utility power network and electric load conductors connected to the residential or building establishment power distribution network. The contacts receive blade terminals on a plug-in watthour meter to complete an electric circuit through the meter between the line and load terminals mounted in the cabinet for the measurement of electrical power consumption.
The meter socket is typically mounted on the rear wall of the cabinet by fasteners, such as or bolts, which extend through the meter socket into the rear wall. Alternately, the meter socket can be mounted on a separate back panel over threaded studs mounted on the rear wall of the cabinet and extending inward through apertures in the panel to receive nuts.
Current transformer or CT rated watthour meters and socket adapters are employed in high current applications. Current transformers coupled to the line and load conductors have their output leads connected to terminals in a current transformer or CT rated watthour meter socket adapter. A low current rated watthour meter is then plugged into the socket adapter to measure power consumed at the building site.
In addition, potential coils in a watthour meter may also be connected via potential blade terminals into potential jaw contacts mounted in the socket adapter and connected by individual conductors to terminals mounted in the terminal portion of the socket adapter.
However, with current transformer rated socket adapters or sockets, it is necessary to short circuit the line and load terminals when the watthour meter is removed from the socket for replacement or testing. Heretofore, bypass devices, which as test switches and slidable link test blocks have been used with CT rated sockets to provide the necessary short circuit or bypass feature.
Exemplary test switches and link test blocks are made by Meter Devices Company, Inc. of Canton, Ohio, the assignee of the present invention. Such bypass devices are typically mounted in a watthour meter socket cabinet immediately below a watthour meter socket. The test switches are generally in the form of single throw, knife-type switches which are provided in multiples ganged together into one assembly; but each electrically connected between one line contact or one load contact in the socket and one current transformer lead. Once an optional socket cover is removed, the test switches can be operated as desired to provide the necessary bypass connection between the line and load contacts and conductors from the current transformers prior to removing the watthour meter from the socket for testing, recalibration, replacement, etc.
Another bypass device is a link test block which is similar to test switches except that a link is removable or slidable between positions to selectively provide the bypass function.
In use, the meter socket itself or along with a bypass device, as shown in FIG. 1, are separately mounted in a socket enclosure or housing. The individual socket terminals are wired to the bypass device terminals.
As shown in FIG. 2, it is also known to mount a meter socket, such as an Ekstrom Industries, Inc., 2100 Series, bottom feed to socket-type adapter on a mounting panel along with a test switch assembly which is separably mounted on the same panel. The meter socket and test switch assembly is then mounted by fasteners on a meter enclosure back panel or in a meter socket housing which extend through apertures in the back panel and receive nuts.
Ekstrom Industries, Inc., has sold a 2100 adapter with built-in or integrally mounted test switches which are mounted below the socket adapter jaw contacts in place of the normal power terminals as shown in U.S. Pat. Nos. 6,475,028 and 6,488,535.
Marwell Corporation has sold a similar 2200 series polyphase A-base to socket adapter with integral mounted test switches as Model Nos. 220-SP-1262. Marwell Corporation has also sold a bi-pass converter adapter, Model No. PTS-13-MTS, which includes a socket mounted in a circular housing which is connected by a sleeve to a meter test switch housing in which the meter test switch is mounted. Conductors pass through the sleeve between the meter jaw contacts and the meter test switch terminals.
While the above-described meter socket and test switches or links provide an effective bypass for use with current transformers in high current load applications, developments in the electrical utility industry pertaining to component ownership and component installation practices have created problems with respect to insuring efficient installation of the proper meter socket and/or meter socket and bypass device at the proper location in a building or use site.
The meter sockets are available in at least three different configurations of jaw contacts for single or three-phase applications, and the presence or absence of potential jaw contacts.
In one ownership/installation scenario, the electric utility owns all of the metering and bypass components and associated socket housings and is responsible for installing the entire assembly at each use site. This requires the utility to maintain a large inventory of the different meter sockets and different bypass devices which results in increased costs to the utility. However, in this situation, the utility company is more likely to install the proper meter socket and bypass device at the proper use location.
In a second ownership/installation situation, the customer owns all of the meter socket and bypass components. A contractor buys the meter socket enclosure, the meter socket and the bypass device from an electrical distributor. These components may be separate or pre-assembled and wired in the socket enclosure or separately mounted in the enclosure and wired by the contractor before the contractor mounts the enclosure at the use site. Frequently, however, due to lack of experience and other factors, the contractor will mount the meter socket and bypass device configuration in the wrong location in a use site or the incorrect socket and bypass device at a given location. This requires replacement of the meter socket and/or the bypass device by the utility or by the contractor at a later date.
In a third ownership/installation situation, the contractor purchases the socket enclosure from an electrical distributor and installs it at a particular location in the use site. The utility then mounts and wires the meter socket and the bypass device in the enclosure at the use site. The mounting of the meter socket and the bypass device in the enclosure by the utility can be done by mounting a pre-wired meter block and bypass device attached to a back panel on the rear wall of a mounted enclosure on four threaded studs or screws extending through the back wall and the panel into the interior of the enclosure. This requires the proper tool operated fasteners, such as nuts, and takes additional assembly time.
The added time and cost of replacing an improperly configured meter socket and bypass device in the field or the time involved in mounting the panel in the enclosure increases the overall costs of the assembly.
Thus, it would be desirable to provide a meter socket and/or a combined meter socket and bypass device apparatus which overcomes the above-described deficiencies occurring with the use of prior art meter socket assemblies. It would also be desirable to provide a meter socket and/or meter socket and bypass device which can quickly be mounted or removed from an enclosure at a use site.